2 Frog Serene Mineral Replacement Cartridges for Hot Tubs for use only with Frog Serene in-Line and Floating Sanitizing Systems for Spas up to 600 gallons, Quick and Easy Hot Tub Sanitizer
2 Pack: Mineral Spa Frog Replacement - 2 Pack: Mineral Spa Frog Replacement * Compared to the minimum EPA recommended bromine level of 1.0 ppm for a stabilized spa.